Method and system for monitoring signal integrity in a distributed controls system

ABSTRACT

A method to monitor integrity of a signal in a distributed control system for a powertrain system includes communications link transmitting signals between control modules. Integrity of each of the control modules is monitored. The signal is generated and verified in an originating control module and transmitted to a receiving control module whereat it is subsequently verified.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/982,453, filed on Oct. 25, 2007 which is hereby incorporated hereinby reference.

TECHNICAL FIELD

This disclosure pertains to control systems for hybrid powertrainsystems.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Known hybrid powertrain architectures can include multipletorque-generative devices, including internal combustion engines andnon-combustion machines, e.g., electric machines, which transmit torquethrough a transmission device to an output member. One exemplary hybridpowertrain includes a two-mode, compound-split, electro-mechanicaltransmission which utilizes an input member for receiving tractivetorque from a prime mover power source, preferably an internalcombustion engine, and an output member. The output member can beoperatively connected to a driveline for a motor vehicle fortransmitting tractive torque thereto. Machines, operative as motors orgenerators, can generate torque inputs to the transmission independentlyof a torque input from the internal combustion engine. The machines maytransform vehicle kinetic energy transmitted through the vehicledriveline to energy that is storable in an energy storage device. Acontrol system is operative to monitor various inputs from the vehicleand the operator and provides operational control of the hybridpowertrain, including controlling transmission operating state and gearshifting, controlling the torque-generative devices, and regulating thepower interchange among the energy storage device and the machines tomanage outputs of the transmission, including torque and rotationalspeed. A control system can monitor input and control signals andexecute algorithms to verify and secure operation of the powertrain.

SUMMARY

A powertrain system includes an engine, a transmission and a torquegenerating machine connected to an energy storage device. Thetransmission is operative to transfer power between the engine and thetorque generating machine and an output member. A method to monitorintegrity of a signal generated and communicated in the control systemincludes establishing a distributed control module system comprising afirst control module operatively connected to the engine, a secondcontrol module operatively connected to the torque generating device, athird control module operatively connected to the transmission device,and a hybrid control module operative to command operation of the first,second, and third control modules. A communications link is establishedto transmit the signal between the first control module, the secondcontrol module, the third control module and the hybrid control moduleand a user interface. Integrity of each of the first, second, third, andhybrid control modules is monitored. The signal is generated in anoriginating control module comprising one of the first, second, thirdand hybrid control modules. Integrity of the signal within theoriginating control module is verified. The signal is transmitted viathe communications link to a receiving control module comprising one ofthe first, second, third and hybrid control modules that is not theoriginating control module. Integrity of the transmitted signal withinthe receiving control module is verified.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an exemplary hybrid powertrain, inaccordance with the present disclosure;

FIGS. 2 and 3 are schematic diagrams of an exemplary architecture for acontrol system and hybrid powertrain, in accordance with the presentdisclosure; and

FIGS. 4 and 5 are schematic flow diagrams of a control scheme, inaccordance with the present disclosure.

DETAILED DESCRIPTION

Referring now to the drawings, wherein the showings are for the purposeof illustrating certain exemplary embodiments only and not for thepurpose of limiting the same, FIGS. 1 and 2 depict an exemplaryelectro-mechanical hybrid powertrain. The exemplary electro-mechanicalhybrid powertrain in accordance with the present disclosure is depictedin FIG. 1, comprising a two-mode, compound-split, electro-mechanicalhybrid transmission 10 operatively connected to an engine 14 and torquemachines comprising first and second electric machines (‘MG-A’) 56 and(‘MG-B’) 72. The engine 14 and first and second electric machines 56 and72 each generate mechanical power which can be transferred to thetransmission 10. The power generated by the engine 14 and the first andsecond electric machines 56 and 72 and transferred to the transmission10 is described in terms of input and motor torques, referred to hereinas T_(I), T_(A), and T_(B) respectively, and speed, referred to hereinas N_(I), N_(A), and N_(B), respectively.

The exemplary engine 14 comprises a multi-cylinder internal combustionengine selectively operative in several states to transfer torque to thetransmission 10 via an input member 12, and can be either aspark-ignition or a compression-ignition engine. The engine 14 includesa crankshaft (not shown) operatively coupled to the input member 12 ofthe transmission 10. A rotational speed sensor 11 monitors rotationalspeed of the input member 12. Power output from the engine 14,comprising rotational speed and engine torque, can differ from the inputspeed N_(I) and the input torque T_(I) to the transmission 10 due toplacement of torque-consuming components on the input member 12 betweenthe engine 14 and the transmission 10, e.g., a hydraulic pump (notshown) and/or a torque management device (not shown).

The exemplary transmission 10 comprises three planetary-gear sets 24, 26and 28, and four selectively engageable torque-transferring devices,i.e., clutches C1 70, C2 62, C3 73, and C4 75. As used herein, clutchesrefer to any type of friction torque transfer device including single orcompound plate clutches or packs, band clutches, and brakes, forexample. A hydraulic control circuit (‘HYD’) 42, preferably controlledby a transmission control module (hereafter ‘TCM’) 17, is operative tocontrol clutch states. Clutches C2 62 and C4 75 preferably comprisehydraulically-applied rotating friction clutches. Clutches C1 70 and C373 preferably comprise hydraulically-controlled stationary devices thatcan be selectively grounded to a transmission case 68. Each of theclutches C1 70, C2 62, C3 73, and C4 75 is preferably hydraulicallyapplied, selectively receiving pressurized hydraulic fluid via thehydraulic control circuit 42.

The first and second electric machines 56 and 72 preferably comprisethree-phase AC machines, each including a stator (not shown) and a rotor(not shown), and respective resolvers 80 and 82. The motor stator foreach machine is grounded to an outer portion of the transmission case68, and includes a stator core with coiled electrical windings extendingtherefrom. The rotor for the first electric machine 56 is supported on ahub plate gear that is operatively attached to shaft 60 via the secondplanetary gear set 26. The rotor for the second electric machine 72 isfixedly attached to a sleeve shaft hub 66.

Each of the resolvers 80 and 82 preferably comprises a variablereluctance device including a resolver stator (not shown) and a resolverrotor (not shown). The resolvers 80 and 82 are appropriately positionedand assembled on respective ones of the first and second electricmachines 56 and 72. Stators of respective ones of the resolvers 80 and82 are operatively connected to one of the stators for the first andsecond electric machines 56 and 72. The resolver rotors are operativelyconnected to the rotor for the corresponding first and second electricmachines 56 and 72. Each of the resolvers 80 and 82 is signally andoperatively connected to a transmission power inverter control module(hereafter ‘TPIM’) 19, and each senses and monitors rotational positionof the resolver rotor relative to the resolver stator, thus monitoringrotational position of respective ones of first and second electricmachines 56 and 72. Additionally, the signals output from the resolvers80 and 82 are interpreted to provide the rotational speeds for first andsecond electric machines 56 and 72, i.e., N_(A) and N_(B), respectively.

The transmission 10 includes an output member 64, e.g. a shaft, which isoperably connected to a driveline 90 for a vehicle (not shown), toprovide output power to the driveline 90 that is transferred to vehiclewheels 93, one of which is shown in FIG. 1. The output power at theoutput member 64 is characterized in terms of an output rotational speedN_(O) and an output torque T_(O). A transmission output speed sensor 84monitors rotational speed and rotational direction of the output member64. Each of the vehicle wheels 93 is preferably equipped with a sensor94 adapted to monitor wheel speed, the output of which is monitored by acontrol module of a distributed control module system described withrespect to FIG. 2, to determine vehicle speed, and absolute and relativewheel speeds for braking control, traction control, and vehicleacceleration management.

The input torque from the engine 14 and the motor torques from the firstand second electric machines 56 and 72 (T_(I), T_(A), and T_(B)respectively) are generated as a result of energy conversion from fuelor electrical potential stored in an electrical energy storage device(hereafter ‘ESD’) 74. The ESD 74 is high voltage DC-coupled to the TPIM19 via DC transfer conductors 27. The transfer conductors 27 include acontactor switch 38. When the contactor switch 38 is closed, undernormal operation, electric current can flow between the ESD 74 and theTPIM 19. When the contactor switch 38 is opened electric current flowbetween the ESD 74 and the TPIM 19 is interrupted. The TPIM 19 transmitselectrical power to and from the first electric machine 56 through afirst motor control module (‘MCP-A’) 33 using transfer conductors 29,and the TPIM 19 similarly transmits electrical power to and from thesecond electric machine 72 through a second motor control module(‘MCP-B’) 34 using transfer conductors 31 to meet the torque commandsfor the first and second electric machines 56 and 72 in response to themotor torques T_(A) and T_(B). Electrical current is transmitted to andfrom the ESD 74 in accordance with whether the ESD 74 is being chargedor discharged.

The TPIM 19 preferably includes a hybrid control module (hereafter‘HCP’) 5 and the pair of power inverters and respective motor controlmodules 33 and 34 configured to receive the torque commands and controlinverter states therefrom for providing motor drive or regenerationfunctionality to meet the commanded motor torques T_(A) and T_(B). Thepower inverters comprise known complementary three-phase powerelectronics devices, and each includes a plurality of insulated gatebipolar transistors (not shown) for converting DC power from the ESD 74to AC power for powering respective ones of the first and secondelectric machines 56 and 72, by switching at high frequencies. Theinsulated gate bipolar transistors form a switch mode power supplyconfigured to receive control commands. There is typically one pair ofinsulated gate bipolar transistors for each phase of each of thethree-phase electric machines. States of the insulated gate bipolartransistors are controlled to provide motor drive mechanical powergeneration or electric power regeneration functionality. The three-phaseinverters receive or supply DC electric power via DC transfer conductors27 and transform it to or from three-phase AC power, which is conductedto or from the first and second electric machines 56 and 72 foroperation as motors or generators via transfer conductors 29 and 31respectively.

FIGS. 2 and 3 are schematic block diagrams of the distributed controlmodule system of the control system. As used herein, the term ‘controlsystem’ is defined as the control modules, wiring harnesses (not shown),communications links, sensors and actuators that monitor and controloperation of the powertrain system. The control system monitors sensorinputs and commands outputs for controlling the actuators. Thedistributed control module system comprises a subset of overall vehiclecontrol architecture, and provides coordinated system control of theexemplary hybrid powertrain described in FIG. 1. The control systemincludes the distributed control module system for synthesizinginformation and inputs, and executing algorithms to control actuators tomeet control objectives, including objectives related to fuel economy,emissions, performance, drivability, and protection of hardware,including batteries of ESD 74 and the first and second electric machines56 and 72. The distributed control module system includes an enginecontrol module (hereafter ‘ECM’) 23, the TCM 17, a battery pack controlmodule (hereafter ‘BPCM’) 21, and the TPIM 19. The HCP 5 providessupervisory control and coordination of the ECM 23, the TCM 17, the BPCM21, and the TPIM 19. A user interface (‘UI’) 13 is preferably signallyconnected to a plurality of devices through which a vehicle operatorcontrols, directs, and commands operation of the electro-mechanicalhybrid powertrain. The devices include an accelerator pedal 113 (‘AP’),an operator brake pedal 112 (‘BP’), a transmission gear selector 114(‘PRNDL’), and a vehicle speed cruise control (not shown). Thetransmission gear selector 114 may have a discrete number ofoperator-selectable positions, including the rotational direction of theoutput member 64 to enable one of a forward and a reverse direction. Theuser interface 13 can comprise a single device, as shown, oralternatively can comprise a plurality of user interface devicesdirectly connected to the individual control modules (not shown).

The aforementioned control modules communicate with other controlmodules, sensors, and actuators via a communications link comprising alocal area network (hereafter ‘LAN’) bus 6, in this embodiment. The LANbus 6 allows for structured communication between the various controlmodules. The specific communication protocol utilized isapplication-specific. The LAN bus 6 and appropriate protocols providefor robust messaging and multi-control module interfacing between theaforementioned control modules, and other control modules providingfunctionality including e.g., antilock braking, traction control, andvehicle stability. Multiple communications buses may be used to improvecommunications speed and provide some level of signal redundancy andintegrity. Communications between the MCP-A 33 and the HCP 5 and betweenthe MCP-B 34 and the HCP 5 is preferably effected using direct linkspreferably comprising serial peripheral interface (hereafter ‘SPI’)buses 37. Communication between individual control modules can also beeffected using a wireless link, e.g., a short range wireless radiocommunications bus (not shown).

The HCP 5 provides supervisory control of the hybrid powertrain, servingto coordinate operation of the ECM 23, TCM 17, MCP-A 33, MCP-B 34, andBPCM 21. Based upon various command signals from the user interface 13and the hybrid powertrain, including the ESD 74, the HCP 5 determines anoperator torque request, an output torque command, an engine inputtorque command, clutch torque(s) for the applied torque-transferclutches C1 70, C2 62, C3 73, C4 75 of the transmission 10, and themotor torques T_(A) and T_(B) for the first and second electric machines56 and 72. The HCP 5 sends commands to specific control modules toeffect control of the engine 14, transmission 10 and the first andsecond electric machines 56 and 72.

The ECM 23 is operatively connected to the engine 14, and functions toacquire data from sensors and control actuators of the engine 14 over aplurality of discrete lines, shown for simplicity as an aggregatebi-directional interface cable 35. The ECM 23 receives the engine inputtorque command from the HCP 5. The ECM 23 determines the actual engineinput torque, T_(I), provided to the transmission 10 at that point intime based upon monitored engine speed and load, which is communicatedto the HCP 5. The ECM 23 monitors input from the rotational speed sensor11 to determine the engine input speed to the input member 12, whichtranslates to the transmission input speed, N_(I). The ECM 23 monitorsinputs from sensors (not shown) to determine states of other engineoperating parameters including, e.g., a manifold pressure, enginecoolant temperature, ambient air temperature, and ambient pressure. Theengine load can be determined, for example, from the manifold pressure,or alternatively, from monitoring operator input to the acceleratorpedal 113. The ECM 23 generates and communicates control signals tocontrol engine actuators, including, e.g., fuel injectors, ignitionmodules, and throttle control modules, none of which are shown.

The TCM 17 is operatively connected to the transmission 10 and monitorsinputs from sensors (not shown) to determine states of transmissionoperating parameters. The TCM 17 generates and communicates actuatorcontrol signals to control the transmission 10, including controllingthe hydraulic circuit 42. Inputs from the TCM 17 to the HCP 5 includeestimated clutch torques for each of the clutches, i.e., C1 70, C2 62,C3 73, and C4 75, and rotational output speed, N_(O), of the outputmember 64. Other actuators and sensors may be used to provide additionalinformation from the TCM 17 to the HCP 5 for control purposes. The TCM17 monitors inputs from pressure switches (not shown) and selectivelyactuates pressure control solenoids (not shown) and shift solenoids (notshown) of the hydraulic circuit 42 to selectively actuate the variousclutches C1 70, C2 62, C3 73, and C4 75 to achieve various transmissionoperating range states, as described hereinbelow.

The BPCM 21 is signally connected to sensors (not shown) to monitor theESD 74, including states of electrical current and voltage parameters,to provide information indicative of parametric states of the batteriesof the ESD 74 to the HCP 5. The parametric states of the batteriespreferably include battery state-of-charge, battery voltage, batterytemperature, and available battery power, referred to as a range P_(BAT)_(—) _(MIN) to P_(BAT) _(—) _(MAX).

A brake control module (hereafter ‘BrCM’) 22 is operatively connected tofriction brakes (not shown) on each of the vehicle wheels 93. The BrCM22 monitors the operator input to the brake pedal 112 and generatescontrol signals to control the friction brakes and sends a controlsignal to the HCP 5 to operate the first and second electric machines 56and 72 based thereon.

Each of the control modules ECM 23, TCM 17, HCP-5, MCP-A 33, MCP-B 34,BPCM 21, and BrCM 22 is preferably a general-purpose digital computercomprising a microprocessor or central processing unit, storage mediumscomprising read only memory (‘ROM’), random access memory (‘RAM’),electrically programmable read only memory (‘EPROM’), a high speedclock, analog to digital (‘A/D’) and digital to analog (‘D/A’)circuitry, and input/output circuitry and devices (‘I/O’) andappropriate signal conditioning and buffer circuitry. Each of thecontrol modules has a set of control algorithms, comprising residentprogram instructions and calibrations stored in one of the storagemediums and executed to provide the respective functions of eachcomputer. Information transfer between the control modules is preferablyaccomplished using the LAN bus 6 and SPI buses 37. The controlalgorithms are executed during preset loop cycles such that eachalgorithm is executed at least once each loop cycle. Algorithms storedin the non-volatile memory devices are executed by one of the centralprocessing units to monitor inputs from the sensing devices and executecontrol and diagnostic routines to control operation of the actuators,using preset calibrations. Loop cycles are executed at regularintervals, for example each 3.125, 6.25, 12.5, 25 and 100 millisecondsduring ongoing operation of the hybrid powertrain. Alternatively,algorithms may be executed in response to the occurrence of an event.

The exemplary hybrid powertrain selectively operates in one of severalstates that can be described in terms of engine states comprising one ofan engine-on state (‘ON’) and an engine-off state (‘OFF’), andtransmission operating range states comprising a plurality of fixedgears and continuously variable operating modes, described withreference to Table 1, below.

TABLE 1 Engine Transmission Operating Applied Description State RangeState Clutches M1_Eng_Off OFF EVT Mode 1 C1 70 M1_Eng_On ON EVT Mode 1C1 70 G1 ON Fixed Gear Ratio 1 C1 70 C4 75 G2 ON Fixed Gear Ratio 2 C170 C2 62 M2_Eng_Off OFF EVT Mode 2 C2 62 M2_Eng_On ON EVT Mode 2 C2 62G3 ON Fixed Gear Ratio 3 C2 62 C4 75 G4 ON Fixed Gear Ratio 4 C2 62 C373

Each of the transmission operating range states is described in thetable and indicates which of the specific clutches C1 70, C2 62, C3 73,and C4 75 are applied for each of the operating range states. A firstcontinuously variable mode, i.e., EVT Mode 1, or M1, is selected byapplying clutch C1 70 only in order to “ground” the outer gear member ofthe third planetary gear set 28. The engine state can be one of ON(‘M1_Eng_On’) or OFF (‘M1_Eng_Off’). A second continuously variablemode, i.e., EVT Mode 2, or M2, is selected by applying clutch C2 62 onlyto connect the shaft 60 to the carrier of the third planetary gear set28. The engine state can be one of ON (‘M2_Eng_On’) or OFF(‘M2_Eng_Off’). For purposes of this description, when the engine stateis OFF, the engine input speed is equal to zero revolutions per minute(‘RPM’), i.e., the engine crankshaft is not rotating. A fixed gearoperation provides a fixed ratio operation of input-to-output speed ofthe transmission 10, i.e., N_(I)/N_(O). A first fixed gear operation(‘G1’) is selected by applying clutches C1 70 and C4 75. A second fixedgear operation (‘G2’) is selected by applying clutches C1 70 and C2 62.A third fixed gear operation (‘G3’) is selected by applying clutches C262 and C4 75. A fourth fixed gear operation (‘G4’) is selected byapplying clutches C2 62 and C3 73. The fixed ratio operation ofinput-to-output speed increases with increased fixed gear operation dueto decreased gear ratios in the planetary gears 24, 26, and 28. Therotational speeds of the first and second electric machines 56 and 72,N_(A) and N_(B) respectively, are dependent on internal rotation of themechanism as defined by the clutching and are proportional to the inputspeed measured at the input member 12.

In response to operator input via the accelerator pedal 113 and brakepedal 112 as captured by the user interface 13, the HCP 5 and one ormore of the other control modules determine torque commands to controlthe torque actuators to meet the operator torque request at the outputmember 64 for transference to the driveline 90. The torque actuatorspreferably include a plurality of torque generative devices, e.g., theengine 14 and the first and second electric machines 56 and 72 and atorque transferring device comprising the transmission 10 in thisembodiment. The HCP 5 determines the operator torque request, an outputtorque command from the transmission 10 to the driveline 90 and actuatorcontrols including an input torque command from the engine 14, clutchtorques for the torque-transfer clutches C1 70, C2 62, C3 73, C4 75 ofthe transmission 10 and motor torque commands for the first and secondelectric machines 56 and 72 based upon operator commands from the userinterface 13.

FIG. 4 shows an embodiment of an architecture to control and managesignal flow in a powertrain system including torque actuators comprisingmultiple torque generating devices and a torque transferring device tocontrol and manage torque transfer and power flow. The architecture isdescribed with reference to, but not limited by, the powertrain systemdescribed hereinabove. The flow of signals through the control modulescontrols the torque generating devices and the torque transferringdevice. In operation, the operator inputs to the accelerator pedal 113and the brake pedal 112 are monitored to determine the operator commandcomprising the operator torque request (‘To_req’). Operation of theengine 14 and the transmission 10 are monitored to determine the inputspeed (‘Ni’) and the output speed (‘No’). A strategic optimizationcontrol scheme (‘Strategic Control’) 310 determines a preferred inputspeed (‘Ni_Des’) and a preferred engine state and transmission operatingrange state (‘Hybrid Range State Des’) based upon the output speed andthe operator torque request, and optimized based upon other operatingparameters of the hybrid powertrain, including battery power limits andresponse limits of the engine 14, the transmission 10, and the first andsecond electric machines 56 and 72. The strategic optimization controlscheme 310 is preferably executed by the HCP 5 during each 100 ms loopcycle and each 25 ms loop cycle.

The outputs of the strategic optimization control scheme 310 are used ina shift execution and engine start/stop control scheme (‘Shift Executionand Engine Start/Stop’) 320 to change the transmission operation(‘Transmission Commands’) including changing the operating range state.This includes commanding execution of a change in the operating rangestate if the preferred operating range state is different from thepresent operating range state by commanding changes in application ofone or more of the clutches C1 70, C2 62, C3 73, and C4 75 and othertransmission commands. The present operating range state (‘Hybrid RangeState Actual’) and an input speed profile (‘Ni_Prof’) can be determined.The input speed profile is an estimate of an upcoming input speed andpreferably comprises a scalar parametric value that is a targeted inputspeed for the forthcoming loop cycle. The engine operating commands arebased upon the input speed profile and the operator torque requestduring a transition in the operating range state of the transmission.

A tactical control scheme (‘Tactical Control and Operation’) 330 isrepeatedly executed during one of the control loop cycles to determineengine commands (‘Engine Commands’) for operating the engine, includinga preferred input torque from the engine 14 to the transmission 10 basedupon the sensor inputs comprising output speed, the input speed, and theoperator torque request and the present operating range state for thetransmission. A clutch torque (‘Tcl’) for each clutch is estimated inthe TCM 17, including the presently applied clutches and the non-appliedclutches, and a present engine input torque (‘Ti’) reacting with theinput member 12 is determined in the ECM 23. A motor torque controlscheme (‘Output and Motor Torque Determination’) 340 is executed todetermine the preferred output torque from the powertrain (‘To_cmd’),which includes motor torque commands (‘T_(A)’, ‘T_(B)’) for controllingthe first and second electric machines 56 and 72 in this embodiment. Thepreferred output torque is based upon the estimated clutch torque(s) foreach of the clutches, the present input torque from the engine 14, thepresent operating range state, the input speed, the operator torquerequest, and the input speed profile. The first and second electricmachines 56 and 72 are controlled through the MCP-A 33 and MCP-B 34 tomeet the preferred motor torque commands based upon the preferred outputtorque.

Securing and monitoring signal integrity to effect torque security isdescribed hereinbelow with reference to the hybrid powertrain systemshown in FIGS. 1, 2, 3, and 4, and resides in the aforementioneddistributed control modules in the form of executable algorithms andcalibrations. The architecture can be applied to powertrain systemshaving multiple torque generating devices, including, e.g., anelectro-mechanical powertrain system having an engine and a singleelectric machine, a hybrid powertrain system having multiple electricmachines, and hydraulic-mechanical hybrid powertrain systems.Controlling and managing the torque and power flow includes monitoringcontrol system hardware, algorithms, and signal integrity.

Torque security of the hybrid powertrain system can be achieved byexecuting integrity tests of the control system which include monitoringhardware integrity of the control system, including the wiring harnesses(not shown), communications links, sensors and actuators that monitorand control operation of the powertrain system. Torque security can beachieved by monitoring integrity of algorithms and memory devices,securing and monitoring signal integrity during communications within acontrol module and communications between the control modules,monitoring integrity of the individual control modules and processors,and executing remedial actions. Torque security in the presence of anobserved fault can include limiting an actuator command signal. This caninclude maximum and minimum limits on actuator command signals, andmaximum rates of change on actuator command signals. Specifically, motortorque commands T_(A) and T_(B) can be limited to maximum and minimummotor torques, and changes in the motor torque commands T_(A) and T_(B)can be limited to effect a maximum rate of change in output torque,e.g., 0.2 g.

Securing and monitoring signal integrity is preferably accomplished byindividually securing the control modules and securing the serialcommunications links between the control modules. The distributedcontrol module system of the embodiment preferably includes each of thetorque actuators controlled by a separate control module. Thisembodiment includes the ECM 23 that monitors sensors and controlactuators of the engine 14, the TCM 17 that monitors sensors and controlactuators of the transmission 10, the MCP-A 33 that monitors sensors andcontrol actuators of the first electric machine 56, and the MCP-B 34that monitors sensors and control actuators of the second electricmachine 72. The HCP 5 monitors inputs from and commands operation of theECM 23, TCM 17, MCP-A 33 and MCP-B 34. The control modules communicatethe signals using the LAN bus 6 and the SPI bus 37. Each of the ECM 23,MCP-A 33, MCP-B 34 and TCM 17, is responsible for closed loop monitoringand self-security based on secured commands received from the HCP 5.

Securing and monitoring integrity of the signal includes monitoringprocessor integrity for each of the control modules. The processorintegrity can be determined using diagnostics software that monitorsdata internal to the control module, and rationalizing it in one of theloop cycles. When an inconsistency between monitored data andrationalized data is detected, the inconsistency is recorded as amismatch or a fault in a fault maturation algorithm, e.g., an X of Yroutine wherein a matured fault is detected when X faults are observedout of immediately preceding Y observations of the signal. An example isdetecting a matured fault when more than half the immediately precedingobservations are mismatches occurring between the monitored data and therationalized data. When the fault maturation algorithm achieves athreshold number of mismatching observations in the immediatelypreceding observations, the fault has matured, indicating signalcorruption and a requirement for remedial action. The remedial actioncan be actuator-specific or across the entire control system, and placesthe powertrain in a torque-safe state. The remedial action will alsoinclude storing an OBD compliant code for subsequent retrieval. Adiagnostic may preliminarily identify a fault pending, meaning aninconsistency has been detected but the fault maturation algorithm hasnot reached its threshold. The hardware integrity can be furtherdetermined using diagnostics software that monitors the sensors andactuators of the control system.

Monitoring integrity of a signal that is generated and communicated inthe control system comprises actions to determine whether a receivedsignal matches the generated signal. A signal can include an operatorcommand signal, a sensor input signal and an actuator command andcontrol signal. With reference to the embodiment described hereinabove,a signal can comprise an actuator command or control signal, including,e.g., motor torque commands for the first and second electric machines56 and 72, the input torque command to the engine 14, and clutch torquecommands for the clutches C1 70, C2 62, C3 73, and C4 75 of thetransmission 10. The signal can include the sensor input signal, e.g., asignal from the rotational speed sensor 11 and the transmission outputspeed sensor 84 and resolvers 80 and 82. The signal can include anoperator command, e.g., an operator input to the accelerator pedal 113,the operator brake pedal 112 and the transmission gear selector 114.

When a signal is generated in an originating control module, the signalis verified within the originating control module prior to transmittingit. The signal is transmitted via one of the communications links to areceiving control module. The transmitted signal is verified in thereceiving control module prior to using it for command or otheroperation in the receiving control module. The signal can includeoperator command signals including the operator inputs to theaccelerator pedal 113, the operator brake pedal 112, the transmissiongear selector 114 and the vehicle speed cruise control. The signal caninclude sensor input signals comprising states of operating parametersdetermined from sensor inputs. The signal can include actuator commandand control signals.

Securing and monitoring integrity of the signal includes verifying firstand second memory locations in a memory device of the originatingcontrol module, and verifying the signal by redundantly storing thesignal at the first and second memory locations in a memory device. Theredundantly stored signals at the first and second memory locations canbe compared immediately prior to transmitting the redundantly storedsignals. Securing and monitoring integrity of the signal includestransmitting the redundantly stored signals via the communications linkto the receiving control module, which receives and stores thetransmitted redundantly stored signals in first and second memorylocations. The transmitted signal is verified in the receiving controlmodule by comparing the transmitted redundantly stored signals stored infirst and second memory locations within the receiving control module.Corruption of the signal within either the originating control module orthe receiving control module can be determined when a difference betweenthe redundantly stored signals is greater than a threshold, leading thecontrol module to execute remedial action.

Monitoring integrity of a signal that is generated and communicated inthe control system comprises actions to determine whether a receivedsignal matches the original signal. A signal can include an operatorcommand signal, a sensor input signal and an actuator command andcontrol signal. With reference to the embodiment described hereinabove,a signal can comprise an actuator command or control signal, including,e.g., motor torque commands for the first and second electric machines56 and 72, the input torque command to the engine 14, and clutch torquecommands for the clutches C1 70, C2 62, C3 73, and C4 75 of thetransmission 10. The signal can include the sensor input signal, e.g., asignal from the rotational speed sensor 11 and the transmission outputspeed sensor 84 and resolvers 80 and 82. The signal can include anoperator command, e.g., an operator input to the accelerator pedal 113,the operator brake pedal 112 and the transmission gear selector 114.

Securing and verifying integrity of a signal that is communicated froman originating control module to a receiving control module ispreferably effected by using redundant data comprising primary andsecondary signals, rationalizing the primary signal, executing a dualstore function prior to storing the signal, creating and transmitting amessage including the signal from an originating control module to areceiving control module using the communications bus, e.g., LAN bus 6,or SPI bus 37, and receiving and decoding the received message toprimary and secondary signals. The primary and secondary signals can becompared prior to processing or execution at one of the actuators.

FIG. 5 shows signal flow to secure and verify integrity of an inputsignal to an originating control module, which comprises an input signalgenerated by a sensor signally connected to the originating controlmodule in this depiction. Alternatively, the input signal in theoriginating control module can comprise one of an operator commandsignal and an actuator command and control signal. The input signal isgenerated (502) and is captured as a primary signal 504 and a redundantsignal 504′. This can include the input signal from the sensor convertedto a digital representation of the input from the sensor using ananalog-to-digital converter (not shown) which may be interposed betweenthe sensor and the originating control module. Diagnostics(‘Diagnostics’) are executed on both the primary signal and theredundant signal (506, 506′). Diagnostics can include limit checks thatindicate when the signal is outside of a predetermined operating rangefor the signal, a rationality check of the signal, and other diagnosticscheck that can indicate corruption of the signal. If a corrupted signalis detected (‘Signal Fault’) in either or both the primary signal andthe redundant signal, a default signal is generated (‘Defaulting’) (508,508′) and communicated to a rationality check 510. The default signalpreferably comprises a predetermined signal that is recognizable in thecontrol module as indicating the primary signal or the redundant signalhas been corrupted. When a fault is not detected (‘No Fault’), theprimary and/or the redundant signals are communicated to the rationalitycheck 510. The rationality check 510 compares the primary signal and theredundant signal and identifies a fault (‘Fault’) when there is adifference detected between the primary and redundant signals. When therationality check 510 indicates that the primary signal is valid (‘ValidSignal’), the primary signal is communicated to a dual store function(‘Dual Store’) 511. The dual store function 511 monitors and comparespresent contents in first and second memory locations 512, 512′ toverify integrity of the memory locations, preferably during each 6.25 msloop cycle. When the dual store function 511 verifies integrity of thefirst and second memory locations, i.e., the present contents in thefirst and second memory locations are identical, the primary signal isstored as the primary signal in the first memory location (‘StorePrimary Signal’) (512) and stored as a secondary signal in the secondmemory location (‘Store Secondary Signal’) (512′). The primary signalstored in the first memory location is subsequently communicated to acontrol path (‘Primary Signal To Control Path’). The secondary signalstored in the second memory location is subsequently communicated to asecurity path. (‘Secondary Signal To Security Path’). If there is adifference between the present contents of the memory locations, a fault(‘Fault’) is recorded indicating corruption of one of the first andsecond memory locations.

When the rationality check 510 indicates corruption of one or both ofthe primary and the redundant signals, or the dual store function 511indicates corruption of the present contents of one the first and secondmemory locations 512, 512′ the control system identifies occurrence ofthe fault (‘Fault’). The control system determines whether the corruptedsignal has matured (‘Mature Fault’) (514), and executes remedial action(516) to mitigate risks associated with the presence of the fault. Afault maturation algorithm can be executed, including, e.g., an X of Yroutine wherein a fault has matured when X mismatched signals areobserved out of immediately preceding Y signal observations. An exampleincludes determining a fault has matured when more than half theimmediately preceding observations indicate a corrupted signal.

Monitoring integrity of a signal transmitted over a serial bus includesdetecting missing data, e.g., detecting loss of a message frame andtaking a short term mitigation action and informing the receivingcontrol module that no new data is available. Detecting missing dataalso includes detecting long term loss of communications to one of thecontrol modules and taking a remedial action.

Monitoring integrity of algorithms and memory devices comprisesverifying integrity of algorithmic code, calibrations and variable datastored in the storage mediums of the control modules including, e.g.,ROM, RAM, and EPROMs. Results of the calculations executed in one of thealgorithms are monitored and verified by monitoring functions thatdetect inconsistencies with torque security critical data stored inmemory and transmitted over the serial data communications busses, i.e.,CAN bus 6 and SPI bus 37. Methodologies applied to detect theinconsistencies include utilizing an alive rolling counter and applyinga protection value to signals that are transmitted over a serial databus to detect corruption of data during transfer. Methods furtherinclude redundantly calculating signals and rationalizing the primaryvalue with the redundant value. Methods further include back-calculatinga signal and rationalizing the resultant with the original signal.Methods further include rationalizing an achieved torque value withactual commanded torque value. Monitor software can execute a detectionalgorithm in one of the loop cycles to detect signal inconsistency. Whenan inconsistency between a monitored signal and a rationalized signal isdetected, the inconsistency is recorded as a mismatch count in a faultmaturation algorithm, e.g., an X of Y routine wherein a fault hasmatured when X mismatched signals are observed out of immediatelypreceding Y signal observations. When a fault matures thus indicating afault in the signal, the control system can execute remedial action tomitigate risks associated with the presence of the fault.

Torque security can include limiting an actuator command signal. Thiscan include maximum and minimum limits on actuator command signals, andmaximum rates of change on actuator command signals. Specifically, motortorque commands T_(A) and T_(B) can be limited to maximum and minimummotor torques, and changes in the motor torque commands T_(A) and T_(B)can be limited to maximum rate of change, e.g., 0.2 g.

Monitoring integrity of a signal transmitted over a serial bus includesdetecting missing data, e.g., detecting loss of a message frame andtaking a short term mitigation action and informing the receivingcontrol module that no new data is available. Detecting missing dataalso includes detecting long term loss of communications to one of thecontrol modules and taking a remedial action.

Securing and monitoring integrity of the signal includes monitoringintegrity of the control modules, i.e., the digital computer comprisingthe microprocessor, storage mediums, high speed clock and related signalconditioning and buffer circuitry. This can be determined by executingtest functions to detect inconsistencies in memory, in general purposeand special purpose registers, execution of instructions, programpointer errors, memory addressing errors, timing errors, and others.Test functions include detecting inconsistencies during systeminitialization, detecting inconsistencies during normal execution byrunning a check function in the background, detecting inconsistencies byexecuting a detection algorithm in one of the loop cycles. When a signalinconsistency is detected, the inconsistency is recorded and a remedialaction taken to mitigate risks associated with presence of the fault.The processor integrity can be determined through an interaction betweenthe HCP 5 and one of the other control modules using a seed and keyprocess, where the monitored control module transmits a certain seed tothe HCP 5, and the HCP 5 responds with a key. The key is made up ofresults from a process that monitors the sequence of the functionsexecuted in the HCP 5 and the seed. The monitored control moduleevaluates the key and determines if it is the expected key based on theseed that it sent to the HCP 5. If the returned key does not match theexpected key, an inconsistency is recorded as a fault count in a faultmaturation algorithm, preferably an X of Y routine wherein a fault hasmatured when X mismatches are observed out of immediately preceding Yobservations, thus indicating a corrupted signal. When inconsistenciespersist long enough for the fault maturation algorithm to reach apredetermined threshold, indicating a corrupted signal, remedial actioncan be taken. Remedial action is executed to mitigate risks associatedwith the presence of the fault.

It is understood that modifications are allowable within the scope ofthe disclosure. The disclosure has been described with specificreference to the preferred embodiments and modifications thereto.Further modifications and alterations may occur to others upon readingand understanding the specification. It is intended to include all suchmodifications and alterations insofar as they come within the scope ofthe disclosure.

The invention claimed is:
 1. Method to monitor integrity of a signalgenerated and communicated in a control system for a powertrain systemincluding an engine, a transmission and a torque generating machineconnected to an energy storage device, the transmission operative totransfer power between the engine and the torque generating machine andan output member, the method comprising: establishing a distributedcontrol module system comprising a first control module operativelyconnected to the engine, a second control module operatively connectedto the torque generating machine, a third control module operativelyconnected to the transmission device, and a hybrid control moduleoperative to command operation of the first, second, and third controlmodules; establishing a communications link to transmit the signalbetween any two of the first control module, the second control module,the third control module and the hybrid control module and a userinterface; monitoring integrity of each of the first, second, third, andhybrid control modules; generating the signal in an originating controlmodule comprising one of the first, second, third and hybrid controlmodules; verifying integrity of the signal within the originatingcontrol module; transmitting the signal via the communications link to areceiving control module comprising one of the first, second, third andhybrid control modules that is not the originating control module; andverifying integrity of the transmitted signal within the receivingcontrol module.
 2. The method of claim 1, further comprising verifyingintegrity of the signal within the originating control module byredundantly storing the signal at first and second memory locations in amemory device of the originating control module and comparing theredundantly stored signals at the first and second memory locationsimmediately prior to transmitting the redundantly stored signals.
 3. Themethod of claim 2, further comprising transmitting the redundantlystored signals via the communications link.
 4. The method of claim 3,further comprising receiving and storing the transmitted redundantlystored signals in first and second memory locations in the receivingcontrol module.
 5. The method of claim 2, comprising detectingcorruption of the signal and executing remedial action when a differencebetween the redundantly stored signals is greater than a threshold. 6.The method of claim 4, further comprising verifying integrity of thetransmitted signal within the receiving control module by comparing thetransmitted redundantly stored signals stored in first and second memorylocations within the receiving control module.
 7. The method of claim 6,comprising detecting corruption of the signal when a difference betweenthe transmitted redundantly stored signals is greater than a threshold.8. The method of claim 7, further comprising executing remedial actionupon detecting corruption of the signal.
 9. The method of claim 1,wherein the signal comprises one of an operator command signal, a sensorinput signal, and an actuator control signal.
 10. The method of claim 1,wherein generating the signal in the originating control module furthercomprises monitoring integrity of algorithmic code stored in memory andexecuted in the originating control module.
 11. The method of claim 1,wherein monitoring integrity of the control modules comprises monitoringhardware integrity of the control modules and associated memory devicesand monitoring integrity of algorithms and memory devices.
 12. Themethod of claim 11, further comprising monitoring integrity ofalgorithms and memory devices by verifying integrity of algorithmiccode, calibrations and variable data stored in the memory devices of thecontrol modules.
 13. Method to monitor signal integrity in a controlsystem for a powertrain system including an engine, anelectro-mechanical transmission and a plurality of torque generatingmachines connected to an energy storage device, the electro-mechanicaltransmission operative to transfer power between the engine and thetorque generating machines and an output member, the method comprising:establishing a distributed control module system comprising a firstcontrol module operatively connected to the engine, a plurality ofsecond control modules corresponding to and operatively connected to theplurality of torque generating machines, a third control moduleoperatively connected to the electro-mechanical transmission, and ahybrid control module operative to generate commands to controloperation of the powertrain system; establishing a communications linkbetween the control modules; monitoring hardware integrity of each ofthe control modules; monitoring integrity of memory devices of each ofthe control modules; monitoring integrity of algorithms and memorydevices of the control modules; monitoring communications integrity; andexecuting remedial action upon detection of a fault.
 14. The method ofclaim 13, wherein monitoring communications integrity comprises:generating the signal in an originating control module comprising one ofthe control modules; verifying integrity of the signal within theoriginating control module; transmitting the signal via thecommunications link; receiving the signal at a receiving control modulecomprising one of the control modules that is not the originatingcontrol module; and verifying integrity of the transmitted signal withinthe receiving control module.
 15. The method of claim 14, furthercomprising: storing the signal at first and second memory locations in amemory device of the originating control module; verifying integrity ofthe signals stored at the first and second memory locations within theoriginating control module; establishing a serial communications link totransmit the verified signals; transmitting the verified signals fromthe originating control module through the serial communications link;receiving the transmitted verified signals at the receiving controlmodule; storing the transmitted verified signals at first and secondmemory locations within the receiving control module; and verifyingintegrity of the stored transmitted signals within the receiving controlmodule.
 16. The method of claim 15, wherein the signal comprises anoperator command signal, a sensor input signal, and an actuator controlsignal.
 17. The method of claim 15, further comprising: generating aprimary and a redundant signal; storing the primary signal at the firstmemory location and storing the redundant signal at the second memorylocation; executing diagnostics on the primary signal and the redundantsignal; executing a rationality check on the primary signal and theredundant signal; and executing a fault maturation algorithm to detectsignal corruption based upon the rationality check on the primary signaland the redundant signal.